文献类型：期刊文献

英文题名：Experimental and computational insights into the conformations of tunicyclin E, a new cycloheptapeptide from Psammosilene tunicoides

作者：Tian, Jun-Mian[1]; Ou-Yang, Si-Sheng[2]; Zhang, Xu[3]; Di, Ying-Tong[4]; Jiang, Hua-Liang[2,5]; Li, Hong-Lin[5]; Dai, Wei-Xing[1]; Chen, Ke-Yu[1]; Liu, Mai-Li[3]; Hao, Xiao-Jiang[4]; Shen, Yun-Heng[1]; Luo, Cheng[2]; Zhang, Wei-Dong[1]

机构：[1] Department of Phytochemistry, School of Pharmacy, Second Military Medical University, 325 Guohe Road, Shanghai 200433, China; [2] Drug Discovery and Design Center, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China; [3] Sate Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematic, Chinese Academy of Sciences, Wuhan 430071, China; [4] State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650204, China; [5] School of Pharmacy, East China University of Science and Technology, Shanghai 200237, China

年份：2012

卷号：2

期号：3

起止页码：1126

外文期刊名：RSC Advances

收录：EI(收录号：20121414922469)

语种：英文

外文关键词：Solvents - Isomers - X ray diffraction - Nuclear magnetic resonance - Nuclear magnetic resonance spectroscopy

摘要：Tunicyclin E (1), a new cyclic heptapeptide, cyclo(Pro1-Ser 2-Trp3-Leu4-Val5-Gly 6-Ser7), was isolated from the root of Psammosilene tunicoides. The presence of two sets of resonance signals in its NMR spectra (1a:1b, ～3:1 abundance) indicated that it has two conformations in solution, while only one conformation was found in its crystal state by X-ray diffraction. To explore the molecular basis of the two conformations of 1 in solution and their interconversion mechanism, X-ray diffraction, NMR experiments, and theoretical calculations were performed. The results disclosed that two conformers of 1 in solution were derived from the cis/trans isomers of the Ser7-Pro1 peptide bond (1a, trans; 1b, cis). The fast interconversion of the two conformations in solution is explained by an intramolecular catalysis mechanism and solvent effects. Furthermore, the existence of several unusual pseudo turns characterized for the first time plays a key role for dominant trans conformation in solution. ? 2012 The Royal Society of Chemistry.